Makindo Medical Notes

Related Subjects: Type 1 DM | Type 2 DM | Diabetes in Pregnancy | HbA1c | Diabetic Ketoacidosis (DKA) Adults | Hyperglycaemic Hyperosmolar State (HHS) | Diabetic Nephropathy | Diabetic Retinopathy | Diabetic Neuropathy | Diabetic Amyotrophy | Maturity Onset Diabetes of the Young (MODY) | Diabetes: Complications |

📖 Introduction

• VRII (Variable Rate IV Insulin Infusion) is a reactive tool: it is staff-intensive, finger-prick heavy, and often “playing catch-up.”
• Still vital in the acutely unwell when tight glycaemic control is essential (e.g. post-MI: 4–8 mmol/L; acute stroke or peri-op: 4–11 mmol/L).
• ⚠️ Main risk = hypoglycaemia, especially in sedated or comatose patients ➝ hence stroke units accept slightly higher targets than cardiac units.
• Insulin needs vary with stress, illness, nutrition, and resistance ➝ no sliding scale is perfect. Most escalate if glycaemia not controlled.
• When stress/illness resolves ➝ transition rapidly back to oral agents (T2DM) or regular insulin (T1DM/new diagnosis).

🧪 Blood Glucose Ranges (UK vs US)

• ✅ Normal fasting: 4.0–5.9 mmol/L (72–106 mg/dL)
• ✅ Normal post-meal: 4.0–7.8 mmol/L (72–140 mg/dL)
• ⚠️ Pre-diabetes (fasting): 6.0–6.9 mmol/L (108–124 mg/dL)
• ⚠️ Diabetes (fasting): ≥7.0 mmol/L (≥126 mg/dL)
• 🚨 Hypoglycaemia: <4.0 mmol/L (<72 mg/dL)
• 📍 Random diabetes diagnosis: ≥11.1 mmol/L (≥200 mg/dL)
• 🔥 Marked hyperglycaemia: ≥20 mmol/L (≥360 mg/dL)
• 💀 Severe hyperglycaemia: ≥30 mmol/L (≥540 mg/dL)

💡 Exam Tip: Quote “4–11 mmol/L” as the safe inpatient target, but “4–8 mmol/L” post-MI for tighter control.

💉 Standard VRII Protocol (check local guideline!)

Preparation: 50 units soluble insulin in 49.5 mL 0.9% NaCl via syringe pump. Run alongside 5% dextrose + 40 mmol KCl at 30 mL/hr (unless hyperkalaemic).

• <4 mmol/L (<72 mg/dL): 🚨 Stop infusion, treat hypoglycaemia.
• 4.1–6.0 mmol/L (74–108): 1 mL/hr.
• 6.1–8.0 mmol/L (110–144): 2 mL/hr.
• 8.1–10.0 mmol/L (146–180): 3 mL/hr.
• 10.1–12.0 mmol/L (182–216): 4 mL/hr.
• 12.1–14.0 mmol/L (218–252): 5 mL/hr.
• >14.1 mmol/L (>254): 6 mL/hr for 2h ➝ if persistent, check IV line/cannula and call doctor.

⏩ Transitioning Off VRII

• Calculate insulin used in last 12h ➝ double for 24h requirement.
• Split: 1/3 as intermediate at 22:00, 2/3 as short-acting with meals.
• Switch back to oral therapy (T2DM) or usual regimen (T1DM) as soon as stable.

📊 Monitoring

• Check capillary glucose (BM) hourly while on VRII.
• Electrolytes: monitor K⁺ closely (risk of hypokalaemia with insulin).
• Aim 4–7 mmol/L pre-meal once stabilised.
• Document, adjust promptly, and escalate if unstable.

🎓 Patient Education

• Never stop insulin when unwell ➝ risk of DKA ⚠️.
• Follow “sick-day rules”: maintain hydration, test frequently, seek medical help early.
• Warn about hypoglycaemia signs, especially if elderly or with poor awareness.